Manufacture of mixed nickel and zinc dithiophosphate



tates This invention relates to a novel process for the manufacture of additives particularly suitable for incorporation in mineral oil compositions and more specifically to a process for the manufacture of additives consisting essentially of mixed nickel and zinc dithiophospha-tes.

With the advent of higher compression internal combustion engines and increases in horsepower, much difficulty has been experienced in formulating a suitable oil composition capable of operating under severe conditions to protect efficiently metal surfaces which come in contact with the oil. In an effort to overcome this problem, a wide variety of additive agents such as detergents, antioxidants, anti-wear agents and the like have been proposed for the improvement of lubricating oils. Generally, each additive agent is employed to impart a particular characteristic to the base oil so as to afiord a finished lubricating composition which is oxidation resistant, stable and non-corrosive to bearing metals, and which effectively reduces varnish and sludge-forming tendencies and minimizes frictional and corrosive wear.

Unfortunately, however, while many of the proposed additive agents improve mineral lubricating oils, quite frequently these lubricating oil compositions have not proved to be entirely satisfactory for commercial use since apparently an additive agent which imparts a beneficial effect may impart unpredictable and undesirable wear to a given engine part. For example, a small amount of zinc dithiophosph-ate displays satisfactory oxidation and bearing corrosion inhibiting properties in a mineral lubricating oil. This additive is particularly active in reducing the corrision of copper-lead bearings subjected to severe operating conditions of temperature and pressure. However, a lubricating oil containing a zinc dithiophosphate and a detergent type agent such as for example, basic barium mahogany sulfonate, was found to allow excessive wear of parts such as wrist pins, valvelifters and rocker arm shafts in recent models of valve-in-head engines. Elimination of the zinc dithiophosphate reduced wrist pin and rocker arm shaft wear but, of course, the resulting composition was subject to oxidative deterioration and the bad effects derived therefrom. The subsequent addition of an anti-wear agent such as sulfurized sperm oil to the composition containing the zinc dithiophosphate for practical purposes eliminated wrist pin wear and reduced valve lifter wear but did not solve the rocker arm shaft wear problems. In fact, the antiwear agent increased rocker arm shaft wear of the base mineral oil. Thus both the zinc dithiophosphate and the anti-wear agent caused excessive wear of the rocker arm shaft and as a result this compounded oil had undesirable,

properties. Such has been the case when using many additive agents and hence much difiiculty has been experienced in formulating an engine lubricating oil of satisfactory anti-wear and anti-oxidant properties.

While displaying satisfactory oxidation and bearing corrosion inhibiting properties in mineral lubricating oils, nickel dithiophosphates have not proved entirely satisfactory for commercial applications since apparently the nickel salt allows spalling of the valve lifters. Thus the problem of discovering a satisfactory lubricating oil composition containing the desired corrosion properties without causing wear to wrist pin and valve lifter has long been a source of experimentation and observation.

Patented Nov. 14, 1961 In the present invention We have discovered a novel method of preparing an additive which may be used in mineral lubricating oil compositions, namely a mixed nickel and zinc dithiophosphate. If less than the stoichiometric amount of an inorganic nickel component such as nickel carbonate is added to a dithiophosphoric acid diester and the resulting material is reacted with an inorganic zin-c component such as zinc or zinc oxide a mixed nickel-zinc dithiophosphate is formed. By this initial addition of the nickel component and the subsequent addition of the zinc component substantially superior filtration rates can be obtained. The mixed nickel and zinc dithiophosphates are easily filtered and optimum filtration rates can be maintained over reasonable periods of time. phosphate can be used in lubricating oils to reduce wrist pin and rocker arm shaft wear. Also, this agent inhibits oxidation and deterioration of the oil without causing ucndue wear to any engine part such as the rocker arm shaft of a valve-in-head engine.

In the present invention a nickel compound such as nickel carbonate is reacted with a dithiophosphoric acid diester at a temperature of from about 70 F. to 165 F. The resulting material is then reacted with a zinc component such as zinc oxide at a temperature of about 70 F. to 165 F. The mixed dithiophosphates are then readily separated by filtration. Preferably, prior to the filtration the reaction product is dehydrated until substantially all the water is removed, and a filtering aid can be added to enhance the subsequent filtration. Typical inorganic nickel and zinc components which may be utilized in our invention are the salts of inorganic acids, hydroxides and the metals themselves. In the initial neutralization step the amount of the nickel component added can range from about 25 to preferably about 40 to 60%, of theory (based on neutralizing the dithiophosphoric acid ester) while the Zinc component employed in the subsequent neutralization can be about 25 to 75% of theory, preferably about 40 to 60%. It is preferred to employ about to 98% of theory of the combined metal components. In the neutralization steps it is pre- 'ferred to employ low temperatures to avoid undue hydrolysis of the dithiophosphates by any water present, and the same is true as to any dehydration effected after neutralization. Consequently, it may even be desirable to employ a vacuum dehydration procedure.

The dithiophosphoric acid d-iester may be conventionally prepared by reacting a sulfide of phosphorus such as phosphorus pentasulfide with an alcohol or a phenol. Suitable alcohols which may be employed in preparing the acid esters include aromatic or aliphatic alcohols containing from 4 to 12 carbon atoms such as 4-methylpentanol-2, hexanol, heptanol, etc. Aromatic alcohols or hydroxyl-containing materials which can be reacted with phosphorus sulfide include phenols and alkylated phenols.

The following data show the various filtration rates obtained in the preparation of dithiophosphates which may be used as additives in lubricating oils.

TABLE I RunNo 3 I 4 Percent 1 NiCOa Percent ZnO Filtration Rate (lbs./ft. /hr.)

The above data clearly indicate that mixed nickel-zinc The resulting mixed nickel and zinc dithiodithiophosphates may be produced at a much more rapid rate than nickel dithiophosphate due to the elimination of the filtration difiiculties associated with the nickel salt.

Optimum results are obtained while using an approximately 50/50 molar ratio of nickel to zinc by first adding nickel carbonate to dithiophosphoric acid diester, such as di-(2-methylpentyl-4)dithiophosphoric acid diester, while maintaining a preferred temperature of about 70 F. to 165 P. Then zinc oxide is slowly added while maintaining a preferred temperature of about 70 F. to 165 F. Next the reaction mixture is dehydrated at a temperature below about 300 F., a filter aid such as Supercel (containing essentially diatomaceous silica) is added and the product is filtered. The resulting product is mixed nickel and zinc dithiophosphate.

The following specific examples are not to be considered limiting.

Example I About 89 grams of nickel carbonate is slowly added while stirring to about 1000 grams of 2-methylpentyl-4 dithiophosphoric acid diester while maintaining a maximum temperature of about 148 F. After all the nickel carbonate is added the reaction is then stirred and heated at about 140 F. for about one hour. The reaction is then cooled slightly and 55 grams of zinc oxide is added While maintaining a maximum temperature of about 150 F. When the addition of the zinc oxide is complete the reaction is dehydrated at about 250 F. for a period of about one hour. Then 20 grams of Supercel is added and the product is filtered. The product a mixed nickel and zinc dithiophosphate analyzes as follows:

Percent nickel 3.95 Percent zinc 4.43 Percent phosphorus 9.67 Percent sulfur 19.2

Example II 475 pounds of nickel carbonate is added to 5410 lbs. of 2-methylpentyl-4 dithiophosphoric acid diester during a period of about 1 /2 hours while maintaining a maximum temperature of about 146 F. The reaction is then stirred for about one hour at about 140 F. 325 pounds of zinc oxide is then added over a period of about 3% hours while maintaining a maximum temperature of about 148 F. The temperature is now raised to about 250 F. for a period of approximately one hour then the temperature is lowered to about 215 F. and 100 lbs. of Supercel is added. The product is now filtered. The filtration takes place in a pressure range of from about 30 p.s.i.g. to about 36 p.s.i.:g. Thus a filtration rate of approximately 162 lbs/sq. ft. filter area/hour is obtained. The product nickel-zinc dithiophosphate analyzes as follows:

Percent nickel 3.76 Percent zinc 4.87 Percent sulfur 17.3 Percent phosphorus 9.60

We claim:

1. A process for the manufacture of a mixed nickel and zinc dithiophosphate consisting essentially of reacting at a temperature of about 70 to 165 F., less than the neutralizing stoichiometric amount of a neutralizing inorganic nickel component with a dithiophosphoric acid diester of an alcohol of from 4 to 12 carbon atoms to partially neutralize the acid ester and obtain an intermediate reaction product, reacting at a temperature of about 70 to 165 F. a neutralizing inorganic zinc component with the intermediate reaction product to further neutralize the acid ester and obtain a mixed nickel and zinc dithiophosphate and filtering to separate the mixed dithiophosphate, the amounts of each of said nickel and zinc components being about 25 to 75 percent of theory based on the dithiophosphoric acid diester.

2. A process for the manufacture of a mixed nickel and zinc dithiophosphate consisting essentially of reacting, at a temperature of about 70 to F., less than the neutralizing stoichiometric amount of a neutralizing inorganic nickel component with a dithiophosphoric acid diester of an alcohol of from 4 to 12 carbon atoms to partially neutralize the acid ester and obtain an intermediate reaction product, reacting at a temperature of about 70 to 165 F. a neutralizing inorganic zinc component with the intermediate reaction product to further neutralize the acid ester and obtain a mixed nickel and zinc dithiophosphate and filtering to separate the mixed dithiophosphate, each of said nickel and zinc components being employed in amounts from about 25 to 75 percent of theory based on the dithiophosphoric acid diester and being selected from the group consisting of the nickel and zinc salts of inorganic acids, oxides, hydroxides, and the metals themselves.

3. A process for the manufacture of a mixed nickel and zinc dithiophosphate consisting essentially of reacting, at a temperature of about 70 to 165 F., less than the neutralizing stoichiometric amount of a neutralizing inorganic nickel compound with a dithiophosphoric acid diester of an alcohol of from 4 to 12 carbon atoms to partially neutralize the acid ester and obtain an intermediate reaction product, reacting at a temperature of about 70 to 165 F. a neutralizing inorganic zinc compound with the intermediate reaction product to further neutralize the acid ester and obtain a mixed nickel and zinc dithiophosphate and filtering to separate the mixed dithiophosphate, the amounts of each of said nickel and zinc compounds being about 25 to 75 percent of theory based on the dithiophosphoric acid diester.

4. A process for the manufacture of a mixed nickel and zinc dithiophosphate consisting essentially of reacting, at a temperature of about 70 to 165 F., less than the neutralizing stoichiometric amount of neutralizing nickel carbonate with a dithiophosphoric acid diester of an alcohol of from 4 to 12 carbon atoms to partially neutralize the acid ester and obtain an intermediate reaction product, reacting, at a temperature of about 70 to 165 F neutralizing zinc oxide with the intermediate reaction product to further neutralize the acid ester and obtain a mixed nickel and zinc dithiophosphate, dehydrating the mixed dithiophosphate, and filtering to separate the mixed dithiophosphate, the amounts of each said nickel carbonate and zinc oxide being about 25 to 75 percent of theory based on the dithiophosphoric acid diester.

5. A process for the manufacture of a mixed nickel and zinc dithiophosphate consisting essentially of reacting at a temperature of about 70 to 165 F. less than the neutralizing stoichiometric amount of a neutralizing nickel carbonate with a dithiophosphoric acid diester of an alcohol of from 4 to 12 carbon atoms to partially neutralize the acid ester and obtain an intermediate reaction product, reacting at a temperature of about 70 to 165 F. a neutralizing zinc oxide with the intermediate reaction product to further neutralize the acid ester and obtain a mixed nickel and zinc dithiophosphate and dehydrating and filtering to separate the mixed dithiophosphate, the amounts of each of said nickel carbonate and zinc oxide being about 40 to 60 percent of theory based on the dithiophosphoric acid diester.

6. The method of claim 5 in which the diester is di- (2-methylpentyl-4)-dithiophosphoric acid diester.

References Cited in the file of this patent UNITED STATES PATENTS 2,344,392 Cook et al. Mar. 14, 1944 2,413,332 Musselman Dec. 31, 1946 2,441,587 Musselman May 18, 1948 2,582,958 Brennan et al. Jan. 22, 1952 2,606,872 Gasser et al. Aug. 12, 1952 2,645,613 Adelson et al. July 14, 1953 2,824,063 Verley Feb. 18, 1958 

1. A PROCESS FOR THE MANUFACTURE OF A MIXED NICKEL AND ZINC DITHIOPHOSPHATE CONSISTING ESSENTIALLY OF REACTING AT A TEMPERATURE OF ABOUT 70* TO 165*F., LESS THAN THE NEUTRALIZING STOICHIOMETRIC AMOUNT OF A NEUTRALIZING INORGANIC NICKEL COMPONENT WITH A DITHIOPHOSPHORIC ACID DIESTER OF AN ALCOHOL OF FROM 4 TO 12 CARBON ATOMS TO PARTIALLY NEUTRALIZE THE ACID ESTER AND OBTAIN AN INTERMEDIATE REACTION PRODUCT, REACTING AT A TEMPERATURE OF ABOUT 70* TO 165*F. A NEUTRALIZING INORGANIC ZINC COMPONENT WITH THE INTERMEDIATE REACTION PRODUCT TO FURTHER NEUTRALIZE THE ACID ESTER AND OBTAIN A MIXED NICKEL AND ZINC DITHIOPHOSPHATE AND FILTERING TO SEPARATE THE MIXED DITHIOPHOSPHATE, THE AMOUNTS OF EACH OF SAID NICKEL AND ZINC COMPONENTS BEING ABOUT 25 TO 75 PERCENT OF THEORY BASED ON THE DITHIOPHOSPHORIC ACID DIESTER. 